Counting rare and elusive animals and evaluating their demographic status, are fundamental yet challenging aspects of population ecology and conservation biology. We set out to estimate population size (Nc), genetic effective population size (Ne gen), sex ratio, and movements based on genetic tagging for the threatened Cantabrian capercaillie. We used 9 microsatellite loci to genotype 134 droppings collected at 34 display areas during the breeding season. Using genetic capture-mark-recapture, we estimated 93 individuals (Nc, 95% CI: 70–116) in an area of about 500 km2, with sex ratio biased towards males (1∶1.6). Estimated Ne gen (35.5) was 38% of Nc, notably higher than the published average in wild populations. This capercaillie population is small and well within concern in terms of population viability. By genetic tagging, we detected mostly short movements; just a few males were recaptured between contiguous display areas. Non-invasive surveys of endangered populations have a great potential, yet adequate sample size and location are key to obtain reliable information on conservation status.

No abstract

The Cantabrian capercaillie (Tetrao urogallus cantabricus) is an endangered subspecies of the Western capercaillie, endemic of northern Spain, inhabiting the south-western limit of the species range. Assessing genetic variability and the factors that determine it is crucial in order to develop an effective conservation strategy. In this work, non-invasive samples were collected in some of the best preserved areas inhabited by Cantabrian capercaillie. Nine microsatellite loci and a sexspecific marker were analysed. We included five zones, separated by valleys with different levels of habitat modifications. No evidence of genetic clustering was found which suggests that fragmentation and development in the area do not act as barriers to gene flow. Nonetheless, significant differences among sampling zones were encountered in terms of their allelic frequencies (global F ST = 0.035, p = 0.001). Pairwise F ST comparisons showed differences between all sampling zones included, except between the two ones located in the South (Degaña and Alto Sil). These findings, along with the results of individual based genetic differences, indicate that gene flow among sampling zones might be at least slightly compromised, except between the two zones located in the South. Despite this, the sampling zones seem to exchange migrants at a rate that prevents genetic differentiation to the point of creating clusters. Our results show that the capercaillies in the study area constitute a single interbreeding group, which is an important piece of information that provides support to better understand the dynamics of this endangered subspecies.

Knowing the location and movements of individuals at various temporal and spatial scales is an important facet of behaviour and ecology. In threatened populations, movements that would ensure adequate genetic flow and long term population viability are often challenged by habitat fragmentation. It is also in those endangered populations where capturing and handling individuals to equip them with transmitters or to obtain tissue samples may present additional logistical challenges. DNA-tagging, i.e. individual identification of samples obtained via non-invasive approaches, can reveal certain movement patterns. We used faecal material genetically assigned to individuals to indirectly track movements of a large-bodied, endangered forest bird, Cantabrian capercaillie (Tetrao urogallus cantabricus), for three consecutive mating seasons. We identified 127 individuals, and registered movements of 70 of them (22 females, 48 males). Most movements were relatively short for capercaillie, mostly concentrated around display areas. We did not find differences in movement distances between females and males within mating seasons, or between them. Several longer, inter-valley movements up to 9.9 km of planimetric distance linked distant display areas, showing that both females and males of Cantabrian capercaillie were able to move through the landscape, complementing previous studies on gene flow. Those longer movements may be taking birds outside of the study area, and into historical capercaillie territories, which still include substantial forest cover. Tracking animals via DNA tagging, particularly those on endangered populations, showed clear advantages like non-intrusiveness and potential for sample sizes much larger than via direct handling. However, it also misses out on direct observation and natural history, which would provide key information like social status and timing of movements.